The present invention relates to a finisher having a stapler for stapling stacks of paper sheets distributed to individual bins of a sorter and, more particularly, to a finisher having means for shifting a paper stack to a stapling position.
A finisher for positioning paper sheets sequentially distributed to individual bins of a sorter and stapling each stack of such paper sheets by a stapler has been proposed in various forms in the past. A prerequisite with this type of finisher is that a stack of paper distributed and discharged onto a bin be moved to a stapling position. This prerequisite has customarily been met by use of a mechanism which moves a stapler toward a bin or a mechanism which moves a bin toward a stapler. This kind of scheme, however, increases the overall scale of the finisher. Moreover, since the mechanism, whether it moves a stapler or a bin, does not directly handle a paper stack, it is difficult to maintain the stapling position constant.
To eliminate the above drawbacks, a paper stack may be pulled to the stapling position of a stapler by a paper pulling device, as also proposed in the art. Specifically, a paper pulling device has a pair of chucks for chucking a paper stack and moves them between a chucking position and a stapling position in the horizontal direction. The coactive chucks are rotatable toward each other to grip a paper stack and away from each other to release it. However, paper pulling devices heretofore proposed have some problems left unsolved regarding the applicability thereof to a finisher, as will be described specifically later.